Is always wrong. The first years of a baby's life are incredibly important in bonding and development, and only a moron would entrust that to people who guaranteed will not love their kid. Heck, they may not even like kids, see all of the monstrous daycare workers who abuse toddlers and babies.
Do a lot of these parents have good intentions? Sure, some of them are doing what they have to do to put food on the table and are making necessary sacrifices, for example: killing things is wrong, but one has to eat so hunting is a necessary evil. However, on the other side of the coin a lot of parents do it because momma's "bored" or wants to "make something" of herself and sit in a cubicle all day.
A baby is typically put in a day care because the parents are out having jobs so they can financially support their family - including the baby. If the parents can't work and have to take care of the baby all day, they won't get the money to put a roof over the baby's mouth and food in his/her mouth. Plus, daycares are specifically designed to be able to keep babies.
If a parent wants to pay a sitter for their 4 year old, let them. They are the ones paying for a service and the person providing the service is making their money, so its all good both ways. Don't shame a parent for hiring a sitter for any child over 1 year of age.